1. Field of the Invention
The invention relates to rail maintenance equipment and, more particularly, relates to a tie plate inserting machine for inserting a previously positioned tie plate between a rail and a tie. It additionally relates to a method of inserting a previously positioned tie plate between a rail and a tie.
2. Discussion of the Related Art
Tie plates are widely used in railway installations. Specifically, the rails of a railroad track are usually secured to cross ties by spikes driven through tie plates positioned between the rail and the tie. The heads of the spikes overlap the base of the rail, and the tie plates block the rails from lateral movement.
It is often necessary during railway track maintenance and/or construction operations to insert a tie plate beneath the rail. For instance, in a typical tie replacement operation, the spikes are pulled from the tie plates to release the tie from the opposed rails. A machine then pulls the tie out from beneath the rails, knocking the tie plates loose as the tie is withdrawn. A laborer then retrieves the tie plates with a hook and sets them aside. Another machine then inserts a new tie beneath the lifted rails. One or two operators then reinsert the tie plates on the top surface of the tie. The tie plates are then inserted between the tie and the rails, either manually or using a machine. The rails are then lowered onto the tie plate, and new spikes are driven through the tie plates to anchor the rails to the tie.
Prior manual and machine based tie plate insertion techniques exhibit marked disadvantages.
In traditional manual-based tie plate insertion techniques, a winch or some other device is used to lift the rail from the tie sufficiently to provide clearance for a tie plate. Operators then place the tie plate on the tie adjacent the rails and push the tie plates beneath the rails, sometimes using a tool. Such manually operated tools are disclosed in U.S. Pat. Nos. 3,882,785 to Rowe and 6,595,140 to Madison et al. Inserting tie plates using such tools is very labor intensive, adding significantly to the cost of a tie replacement operation. It is also very time consuming—undesirably increasing the time that a railway is out of service for track maintenance operations.
Other machines have been proposed that position and insert tie plates, either in a stand-alone basis or as part of a larger machine that performs other track maintenance operations. These machines are disclosed, for example, in U.S. Pat. Nos. 5,067,412 to Theurer et al.; 5,655,455 to Smith; and 6,158,353 to Theurer. All three of these machines dispense tie plates from a magazine, position the tie plate adjacent the rail, and drive the tie plate beneath the rail using a complex structure. These machines are very complex and expensive to operate. They also have reliability issues resulting from their complexity. They are also relatively slow. Their insertion tools also lack the freedom of movement required to reliably insert a previously positioned tie plate beneath a rail.
The need therefore has arisen to provide a tie plate inserting machine that is relatively simple to operate yet is capable of reliably and rapidly inserting a prepositioned tie plate beneath a rail.